Variable temperature refrigeration



June 4, 1957 C. S. HERRICK VARIABLE TEMPERATURE REFRIGERATION Filed June29, 1954 3 [)6 Va 77 cprz- Ca r/fy/e 8. fferrick,

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Unite rates Carlyle S. Herrick, Alplaus, N. Y., assignor to GeneralElectric Company, a corporation of New York Application dune 29, 1954,Serial No. 440,623

7 Claims. (Cl. 62-115) This invention relates to refrigeration systemsand specifically to a method and apparatus to secure variabletemperature levels in such systems.

Refrigeration systems, which are capable of providing automatic variabletemperature levels, are desirable in heat pump construction and incommercial and domestic refrigerators. It is desirable that a reverserefrigeration system or heat pump employ a refrigerant mixture whosecomposition is varied automatically to maintain a constant systemcapacity over a wide variation in the evaporator temperatures. Aconventional refrigeration system, which employs a single refrigerant,will not operate at constant capacity over such temperature variations.

Accordingly, it is an object of my invention to provide a new andimproved refrigeration system in which a pair of partly misciblerefrigerants are employed.

It is another object of my invention to provide a refrigeration systemwhich circulates a variable mixture of refrigerants in response to theload upon the system.

It is another object of the invention to provide a refrigeration systemin which the composition of the refrigerant mixture is determined by theevaporator temperature.

It is a further object of the invention to provide a novel method ofrefrigeration in which the composition of the refrigerant mixture in therefrigeration system is varied automatically to produce differenttemperature levels of refrigeration.

In carrying out my invention in one form, the composition of therefrigerant mixture is varied with the evaporator temperature tomaintain a constant capacity refrigeration system.

These and various other objects, features and advantages of theinvention will be better understood from the following description takenin connection with the accompanying drawing in which:

Fig. l is a schematic view of one form of a refrigeration system whichembodies my invention; and

Fig. 2 is a schematic view of a second form of a refrigeration system.

In Fig. 1 of the drawing, a refrigeration system, which may be used inheat pump construction or in commercial or domestic refrigerators andwhich is indicated generally at 10, comprises a compressor 11 whichcommunicates on its high pressure side with a condenser 12. Thecondenser 12 is connected to a liquid running receiver 13 in which apair of partly miscible refrigerants are in a mixture 14 to becirculated through an outlet 15 and an expansion valve 16 to anevaporator 17. The expansion valve 16 is shown to be of a conventionaltype which is operated by a pressure tube 18 and diaphragm 19. Atemperature-operated or thermostatic control valve or sections ofcapillary tubing could be employed as the expansion device. Theevaporator 17 is connected to the inlet or low pressure side of thecompressor 11.

A storage receiver 20 is provided in the system to contain an additionalsupply of the same refrigerants in two separate partly miscible phasesor layers 21 and 22. Each atent of these phases 21 and 22 contain bothrefrigerants in different proportions. The storage receiver 20 isconnected to the liquid receiver 13 through a tube 23 with a liquidcontrol valve 24. A vapor space 25 is provided in the top of receiver 20in which a float 26 may be positioned to actuate valve 24 through asuitable electrical or mechanical connection. A capillary tube 27connects receiver 20 to outlet 15 between expansion valve 16 andevaporator 17 to circulate slowly a continuous stream of refrigerantphase 21 thereto under gravity head. Tube 23 will replenish therefrigerants in receiver 20 from refrigerant mixture 14 in receiver 13.Vapor space 25 in receiver 2t communicates with the inlet side of thecompressor 11 through a tube 28 which is connected to the outlet ofevaporator 17. The pressure and composition of the refrigerants inreceiver 20 determine the temperature therein which is controlled byevaporator pressure through tube 28. In a reversed refrigeration systemor heat pump, the outdoor temperature will regulate indirectly thecomposition of each of the refrigerant phases 21 and 22.

The pair of refrigerants, which are employed in the refrigerationsystem, may be miscible at condenser temperature but must be only partlymiscible at customary evaporator temperatures. The pair of partlymiscible refrigerants forms two separate phases in which each phase isrich in one of the refrigerants and contains also a substantial amountof the second refrigerant. The amount of the second refrigerant in eachphase is controlled by the temperature. It is desirable to have a widevariation of phase composition with temperature in the customaryevaporator temperature range. The two phases must also have differentdensities so that separation is possible by gravity. The pair ofrefrigerants must have difierent volatilities so that the refrigeratingcapacities of the system may be altered.

The following pairs of refrigerants are given as examples of suitablerefrigerant mixtures to be employed in such a variable temperaturesystem: ammonia (NHa) and Freon 12 (CFzClz), ammonia (NI-Ia) and Freon114 (C2F4C1z), ammonia (NI-I3) and perfluorocyclobutane (C4Fs), ammonia(NHa) and Freon 115 (CzFsCl), ammonia (NI-I3) and perfluoropropane(CaFs), sulfur dioxide (S02) and perfluorocyclobutane (CiFa),methylbromide (CH3B1') and perfluorocyclobutane (C4Fa), methylenechloride (CHzClz) and perfluoropropane (CaFs), ethylchloride (C2H5Cl)and perfluoropropane (CsFs), perfluoropropane (CsFs) and methylbromide(CH3Br), perfluoropropane (CaFa) and methylchloride (CI-IaCl),perfluoropropane (CaFa) and Freon 21 (CHFCIz perfluoropropane (CaFs) andFreon 31 (CHzFCl), perfluorobutane (C4Fm) and Freon 21 (CHFClz),perfluorobutane (Cribs) and methylchloride (CHaCl), perfluorobutane(C4F10) and methylene chloride (CHzClz), perfiuorobutane (C4F1n) andethylchloride (C2H5Cl), Freon 115 (CzFsCl) and methylene chloride(CHzClz), and Freon 115 (CzFsCl) and sulfur dioxide (S02).

In the operation of the refrigeration system which is shown in Fig. 1 ofthe drawing, compressor 11 pumps refrigerant mixture 14 throughcondenser 12 to liquid running receiver 13. Refrigerant mixture 14,which is miscible at condenser temperature, is then circulated throughoutlet 15, expansion valve 16, and evaporator 17 to the inlet side ofcompressor 11. The storage receiver 20, in which an additional supply ofmixture 14 is con tained in two separate partly miscible phases 21 and22, is connected to both receiver 13 and outlet 15. The capillary tube27 from the receiver 20 provides a slow, continuous circulation of phase21 to outlet 15 to vary the composition of refrigerant mixture 14 inresponse to the system load. Refrigerant phase 21 is shown to be theoperating phase while phase 22 is the storage phase. An increase in theoutdoor temperature increases the concentration of the low capacityrefrigerant in phase 21 while .a decrease inroutdoor' temperature111161363565 the concentration of the. high capacity refrigerant .inphase 21. Storage .phase .22 gives :up .oraccepts .fthe neces saryquantities of such refrigerants toaffect these .changes. Thus, thecapacity of the refrigeration system remains automatically constant over'a wide rangeof temperature variations with the addition of only phase21. Ifit is desired, phase 22 may be the operating phase While phase 21is the storage phase.

Refrigerant mixture 14 is withdrawn from receiver 13 through tube 23Iandcontrol valve 24 to replenish the refrigerants in receiver 20 which arecirculated to the system from phase 21 thereof. Valve24 may be actuatedby .any'suitable controls, such as, for example, float 26 which ispositioned in receiver 20 and connected mechanically or electrically tovalve 24. The withdrawal of a portion ofphase 21 causes the float 26 tobe depressed downwardly to open the valve 24. The composition ofrefrigerant mixture 14 is determined by the system load through thepressure variations of the evaporator. However, the volume of therefrigerant mixture remains constant in the refrigeration system throughthe addition of refrigerant phase 21 and the corresponding withdrawal ofcirculating mixture 14.

In Fig. 2 of the drawing, a modified refrigeration system is shown inwhich anenlarged tubular section 30 is positioned in tube 23 betweenreceivers 13 and 20. The outlet 15 is provided with a heat exchange coil31 which is positioned within section 30 to cool refrigerant mixture 14which passes from receiver 13 to storage receiver and to separatemixture 14 into refrigerant phases 21 and 22. The cooling of refrigerantmixture 14 reduces the amount thereof which flashes to vapor at valve 24to provide better composition control. The refrigeration system of Fig.2is otherwise similar in structure and operation to the refrigerationsystem which is disclosed inFig. 1.

As will be apparent to those skilled in the art, the objects of myinvention are attained by the use of a refrigerant mixture which isvaried with the evaporator temperature to maintain a constant capacityrefrigeration 'system.

While other modifications of this inventionand variations of apparatuswhich may be employed in 'the scope of the invention have not beendescribed,'the invention is intended to include all such .as maybeembraced within the following claims.

What I .claim as new :and desire to secure by Letters Patenttof theUnited States is:

1. In a refrigeration system including a compressor, a condenser, andanevaporator, a supply of .partlymiscible refrigerants, means tocirculatesaid supply, .a second supply of partly miscible refrigerants inseparate phases, meansto. selectively control the composition of saidphases, means connected to said'second supply and said circulating meansto supply at least one of said phases to said first mentionedrefrigerants to vary the composition thereof, and means to circulate apart of said first refrigerant supply to said second refrigerant supplyto replenish the volume thereof.

2. In a refrigeration system including a compressor, a condenser, and anevaporator, a supply of partly miscible refrigerants, means to circulatesaid supply, a second supply'of partly miscible refrigerants .inseparate phases, means connectedto said second supply and saidcirculating means to supply at least one of said phases to said firstrefrigerants, and means to circulate a partof said first refrigerantsupply to said second refrigerant supply to replenish the volumethereof.

3. In a refrigeration system including a compressor, a condenser, and anevaporator, a pair of liquid receivers, a supply of partly miscible:refrigerants in one of said receivers, means to circulate said supply, asecond supply of partly miscible refrigerants in separate phases in saidsecond receiver, means to selectively control the composition of saidphases, means connected to said second supply and said circulating meansto continuously supply at least one of said phases to said firstrefrigerants to vary the composition thereof, and means connecting thepair of receivers to circulate a part of said first refrigerant supplyso said second receiver.

4. A method of refrigeration which comprises circulating a first supplyof partly miscible refrigerants in a refrigeration system, providing asecond supply of partly miscible refrigerants in separate phases,circulating one of the phases to the first refrigerant supply to changethe composition thereof, and varying the composition of the phases inresponse to the system load.

5. A method of refrigeration which comprises circulating a first supplyof partly miscible refrigerants in a refrigeration system, providing asecond supplyof partly miscible refrigerants in separate phases,circulating one of the phases to the first refrigerant supply to changethe composition thereof, varying the composition of the phases inresponse to the system load, and circulating a part ofthe firstrefrigerant supply to the second refrigerant supply to replenish thevolume thereof.

6. A refrigeration system comprising a -:compressor,ta condenserconnected to said compressor, a liquid receiver connected to saidcondensena supply of partly-miscible refrigerants in said receiver, anevaporatorgmeans .conmeeting said receiver to said evaporator, means:connecting said evaporator to said compressor, a vstorage receiver, asupply of ,partly' miscible refrigerants in separate phases within saidstorage receiver, said storage receiver connected to said liquidreceiver and said connecting means between the liquid receiver and theevap-' orator, and means connecting said storage receiver and saidconnecting means between the evaporator and the compressor toselectively control the composition of the phases within thelstoragereceiver. t

7. A refrigeration system comprising ,,a compressor, a condenserconnected to said compressor, a liquid receiver connected to saidcondenser, a supply of partly miscible refrigerants in said 'creceiver,an evaporator, means connecting said receiver to said evaporator, meansconnecting said evaporator to said=compressor, a storage receiver, asupply of partly miscible refrigerants in separate phases within saidstorage receiver, and cooling means connecting said storage'receiverandsaid liquid receiver, means connecting said storage receiver andsaidconnecting means between the liquid receiver and the evaporator, andmeans connecting said storage receiver and said counecting means betweenthe evaporator and the compressor to selectively control the compositionof the phases within the storage receiver.

References Cited'in the file of-this patent

